Monday, November 22, 2010
Genes and kidney disease in African-Americans
In African Americans with kidney disease related to hypertension (high blood pressure), a common gene variant is associated with a sharply increased risk of progressive kidney disease. End Stage Renal Disease (ESRD) associated with hypertension occurs in the African American population at a rate 13.1 times greater than that of their white counterparts. "We found that individuals with the common genotype were approximately 1.5 times more likely to have progressive kidney disease than those with other genotypes," comments Brad C. Astor, PhD (Johns Hopkins Bloomberg School of Public Health, Baltimore). The variant gene - found in more than half of patients in the study - could contribute to the high rate of ESRD among African Americans. The researchers performed genetic studies to identify variant forms of the gene MYH9 in 706 African Americans with kidney disease related to high blood pressure (hypertensive nephrosclerosis). The patients were drawn from a larger study, the African American Study of Kidney Disease and Hypertension (AASK). "African Americans are at much higher risk of ESRD compared to white Americans, but the reasons for this discrepancy are unknown," Astor explains. "A genetic variation of the MYH9 gene, common in African Americans, was recently found to be associated with ESRD in individuals without diabetes. We examined the association between this genetic variation and progression of kidney disease in African Americans with hypertensive nephrosclerosis." In the AASK patients, several MYH9 gene variants were related to the risk of decreased kidney function or ESRD. Participants with one MYH9 variant were likely to have other variants as well. The same MYH9 gene variant previously linked to nondiabetic ESRD was also associated with an increased risk of progressive kidney disease in the AASK patients. The risk of death, ESRD, or a significant drop in kidney function was 50% higher than in those without the variant gene. The variant MYH9 gene was very common, present in 55% of the AASK study participants. Its association with progressive kidney disease was independent of age, sex, or treatment for high blood pressure. The same variants are present in many African Americans without kidney disease, however. The results add new evidence linking MYH9 variants to racial differences in kidney disease rates and outcomes.